The force or power restoration system according to the invention relates to drive simulators and more particularly to the simulation of vehicle driving members.
For reasons of economy, efficiency and safety, the driving of vehicles and in particular armoured vehicles, is now taught by means of fixed drive simulators, instead of real vehicles.
In these simulators, the driving cabs are faithfully reproduced and are often mounted on moving platforms. By means of the latter, they are subject to movements determined by computers in accordance with the operations or manipulations performed, the state of the road, or that of the ground which it is assumed is being traversed.
The driving members and the like are simulated with respect to their arrangement in the cab, their appearance and also the forces necessary for their operation and the reaction which said members may transmit to the driver.
These driving members have reactions inherent therein, which are dependent on the type of vehicle, the operation taking place, the operating state of the driving member, and the manner in which the latter is actuated. A good knowledge of these reactions permits a better observation of the behaviour of the vehicle and consequently enables more effective action on the driving members. It is therefore vital that it is possible to simulate in a drive simulator, the mechanical reactions of the driving members and also certain of their failures.
The force restoration system according to the invention more specifically relates to the simulation of driving members acting via high pressure hydraulic controls. Thus, for example, it relates to the simulation of braking members and also, in the case of certain armoured vehicles, to the simulation of steering members, whose movements are transmitted by a hydraulic control and lead to braking forces on differential systems.
The use of a real braking system in a drive simulator is not satisfactory due to the unnecessary complexity thereof, its overall dimensions and its cost.
Hydraulic force restoration systems of the type shown in FIG. 1 have already been used in simulators. Their operating principle is similar to that of genuine braking systems. A master cylinder 2 transmits the braking force F, supplied by the driver, to a jack 6 via a pipe 3 and a hydraulic fluid from a tank 1. This fluid actuates the jack and brings about the compression of a stack of commercially available metallic, elastic washers 7, whose elasticity has been determined in such a way as to simulate the elastic expansion of real pipes and the deformation of the brake levers. An electrovalve 4 controlled by a computer C makes it possible, via a pipe 8 which returns the hydraulic fluid to the tank, to eliminate any reaction or "stiffness" opposing the operation of the pedal, as well as to simulate in this way a braking failure due to a hydraulic fluid leak. A pressure transducer 5 transmits the pressure value, which can reach 200 bar, to the computer.
Although apparently being relatively simple, the prior art system is not satisfactory. As a result of the pressure reached, the electrovalve, jack and pressure transducer constitute costly components. Moreover, the jack 6 and the stack of washers 7 form a space-consuming and unduly heavy assembly. Thus, in a driving simulator it may be necessary to use four force restoration systems of this type, namely two for the driving and two for the road and parking brakes. The weight and volume of the components fitted in the cab and, in the circumstances, those of the force restoration systems, obviously condition the performances and price of the moving platform mounted on hydraulic jacks, which moves this assembly. Another disadvantage of this type of force restoration system is that it may give rise to hydraulic fluid leaks in the driving cab.